Abstract
Variation in the location of the 15p region D15Z1 is recognized as a polymorphism in several human populations. We used high-stringency Fluorescence In Situ Hybridization (FISH) to detect D15Z1 in a Mexican cohort. Here, we report the presence of extra D15Z1 sequences on the p-arm of acrocentric chromosomes other than 15 in two groups of Mexican couples, one with healthy offspring (n = 75) and the other with aneuploid offspring (n = 87), mainly trisomy 21. The additional D15Z1 polymorphism was significantly increased in individuals with aneuploid offspring (26.4%), in comparison to individuals with healthy offspring (14%). The most frequent acceptor chromosome of D15Z1 was chromosome 13p, followed by 14p, and finally, 21p. Our results show an overall frequency of 21.6% of this polymorphism in the Mexican population and suggest that its presence might be associated with the mis-segregation of other acrocentric chromosomes and aneuploid offspring. The high frequency of the polymorphism of the D15Z1 sequence on acrocentric chromosomes other than 15 suggests a sequence homogenization of the acrocentric p arms, related to the important function of the centromere and the nucleolar organization region, which flank satellite III DNA.
Highlights
The human acrocentric chromosomes are classified in group D, which includes pairs 13, 14, and 15, and in group G, which includes pairs 21 and 22
The study of acrocentric chromosomes has gained relevance given their involvement in clinically important cytogenetic alterations, such as: (a) aneuploidy, the leading cause of spontaneous abortions and congenital birth defects; (b) marker chromosomes, which are chromosomes that are not identified by banding pattern; and, (c) Robertsonian translocations, formed through the fusion of two acrocentric chromosomes with breakpoints mainly in the proximal short arms [1,2]
We found a significant association between the presence of additional D15Z1 signals and aneuploid offspring, before claiming that a true association between the presence of the polymorphism and an increased risk for chromosome trisomy exists, the following caveats need to be considered: (a) in this study, only a minority of the additional D15Z1 signals was found on chromosome 21p, the chromosome that is involved in aneuploidy of the majority of the offspring
Summary
The human acrocentric chromosomes are classified in group D, which includes pairs 13, 14, and 15, and in group G, which includes pairs 21 and 22. The study of acrocentric chromosomes has gained relevance given their involvement in clinically important cytogenetic alterations, such as: (a) aneuploidy, the leading cause of spontaneous abortions and congenital birth defects; (b) marker chromosomes, which are chromosomes that are not identified by banding pattern; and, (c) Robertsonian translocations, formed through the fusion of two acrocentric chromosomes with breakpoints mainly in the proximal short arms [1,2]. All three of these cytogenetic alterations are important for human health. Robertsonian translocations are the most frequent chromosomal rearrangement in humans with a frequency of 1/1000 individuals [13,14]
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